Methods and systems of tagging objects and reading tags coupled to objects

ABSTRACT

Methods and systems of tagging objects and reading tags coupled to objects. At least some of the illustrative embodiments are systems comprising a reading antenna, a tag reader coupled to the reading antenna, and a radio frequency identification (RFID) tag comprising a tag antenna electromagnetically coupled to the reading antenna. The RFID tag couples to an object such as the body of a living organism or a metallic article. Moreover, the tag antenna has a far-field radiation pattern in a direction away from the object that is substantially unaffected by proximity of the RFID tag to the object, and substantially unaffected by which surface of the RFID tag faces the object.

BACKGROUND

1. Field

The various embodiments are directed to radio frequency identification(RFID) tags for use with metallic articles and/or bodies of livingorganism, and systems for reading RFID tags.

2. Description of the Related Art

Radio frequency identification (RFID) tags are used in a variety ofapplications, such as goods identification in wholesale and retailsales, access cards (e.g., building access, garage access), and badgingand identification of employees. However, many industries have been slowto adopt the use RFID tags. For example, the cattle industry has beenslow to adopt RFID tags as a means to identify particular animalsbecause of difficulties in reading the RFID tags. In particular,depending on the physical placement of the RFID tag, the body of theanimal may block the ability of a tag reader to read the RFID tag.Moreover, placing the antenna (e.g., loop or dipole antenna) of an RFIDtag close to the body of the animal adversely affects the ability of theantenna to receive power, and also adversely affects the tag's abilityto radiate power (for active tags) or reflect power (for passive tags).The same shortcomings affect industries where the underlying product ismetallic.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of various embodiments, reference will now bemade to the accompanying drawings in which:

FIG. 1 shows a system in accordance with at least some embodiments;

FIG. 2 shows a dual-sided patch antenna in accordance with at least someembodiments;

FIGS. 3A and 3B show far-field radiation (or reception) patterns for theantenna elements of the dual-sided patch antenna consideredindividually;

FIG. 4 shows the far-field radiation (or reception) pattern for thedual-sided patch antenna of various embodiments;

FIG. 5 shows an electrical block diagram of circuitry for coupling tothe dual-sided patch antenna in accordance with at least someembodiments;

FIG. 6 shows an electrical block diagram of circuitry for coupling tothe dual-sided antenna in alternative embodiments;

FIG. 7 shows an elevational, cross-sectional view of a badge comprisingdual-sided patch antenna proximate to a body;

FIG. 8 shows an electrical block diagram of circuitry for coupling tothe dual-sided antenna in further alternative embodiments;

FIG. 9 shows a perspective view of an arrangement of reading antennas inaccordance with at least some embodiments;

FIG. 10 shows an elevational view of an arrangement of reading antennasin accordance with alternative embodiments;

FIG. 11 shows an overhead view of an arrangement of reading antennas inaccordance with alternative embodiments;

FIGS. 12A and 12B show electrical block diagrams of various embodimentsof coupling reading antennas to readers; and

FIG. 13 shows a method in accordance with at least some embodiments.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claimsto refer to particular system components. As one skilled in the art willappreciate, design and manufacturing companies may refer to a componentby different names. This document does not intend to distinguish betweencomponents that differ in name but not function. In the followingdiscussion and in the claims, the terms “including” and “comprising” areused in an open-ended fashion, and thus should be interpreted to mean“including, but not limited to . . . .”

Also, the term “couple” or “couples” is intended to mean either anindirect or direct connection. Thus, if a first device couples to asecond device, that connection may be through a direct connection orthrough an indirect connection via other intermediate devices andconnections. Moreover, the term “system” means “one or more components”combined together. Thus, a system can comprise an “entire system,”“subsystems” within the system, a radio frequency identification (RFID)tag, a RFID reader, or any other device comprising one or morecomponents.

DETAILED DESCRIPTION

The various embodiments disclosed herein are discussed in the context ofradio frequency identification (RFID) tags; however, the systems andmethods discussed herein have application beyond RFID tags to othertypes of radio frequency technologies. The discussion of any embodimentin relation to RFID tags is meant only to be illustrative of thatembodiment, and not intended to intimate that the scope of thedisclosure, including the claims, is limited to that embodiment.

FIG. 1 illustrates a system 1000 in accordance with at least someembodiments. In particular, system 1000 comprises an electronic system10 coupled to a RFID reader 12. In some embodiments, electronic system10 comprises a computer system. By way of antenna 14, the RFID reader 12communicates with one or more RFID tags 16A-16C (each having antenna17A-17C as shown) proximate to the RFID reader (i.e., withincommunication range). The RFID reader 12 may be equivalently referred asan interrogator. The RFID reader 12 passes data obtained from thevarious RFID tags 16 to the electronic system 10, which performs anysuitable function. For example, the electronic system 10, based on thedata received from the RFID tags 16, may allow access to a building orparking garage, note the entrance of an employee to a work location,direct a parcel identified by the RFID tag 16 down a particular conveyorsystem, or display an advertisement customized or targeted to the personidentified by the RFID tag 16.

There are several types of RFID tags operable in the illustrative system1000. For example, RFID tags may be active tags, meaning each RFID tagcomprises its own internal battery. Using power from the internalbattery, an active RFID tag monitors for interrogating signals from theRFID reader 12. When an interrogating signal is sensed, a responsecomprising a data or identification value is transmitted by the activeRFID tag using power from its internal battery. A semi-active tag maylikewise have its own internal battery, but a semi-active tag staysdormant most of the time. When an antenna of a semi-active tag receivesan interrogating signal, the power received is used to wake or activatethe semi-active tag, and a response comprising an identification valueis sent by the semi-active RFID tag using power from its internalbattery.

A third type of RFID tag is a passive tag, which, unlike active andsemi-active RFID tags, has no internal battery. The antenna of thepassive RFID tag receives an interrogating signal, and the powerextracted from the received interrogating signal is used to power thetag. Once powered, the passive RFID tag may either of both of accept acommand, or send a response comprising a data or identification value;however, the value is sent in the form of backscattered electromagneticwaves to the RFID reader 12 antenna 14 from the antenna 17 of the RFIDtag 16. In particular, the RFID reader 12 and antenna 14 continue totransmit power after the RFID tag is awake. While the RFID reader 12transmits, the antenna 17 of the RFID tag is selectively tuned andde-tuned with respect to the carrier frequency. When tuned, significantincident power is absorbed by the antenna 17 of the RFID tag 16 (and isused to power the underlying circuits). When de-tuned, significant poweris reflected by the antenna 17 of the RFID tag 16 to the antenna 14 ofthe RFID reader 12. The data or identification value thus modulates thecarrier in the form of reflected or backscattered electromagnetic wave.The RFID reader 12 reads the data or identification value from thebackscattered electromagnetic waves. Thus, in this specification and inthe claims, the terms transmitting and transmission include not onlysending from an antenna using internally sourced power, but also sendingin the form of backscattered signals.

Regardless of the type of RFID tag used (i.e., active, semi-active orpassive) for the RFID reader 12 to interrogate the tag and receivereturn data, the antenna 17 of the RFID tag 16 is tuned to substantiallythe proper frequency, and the antenna directivity of the RFID tag 16 isin at least partial alignment with directivity of the antenna 14 of theRFID reader 12. However, dipole antennas and loop antennas tuned forfree space tend to de-tune when placed proximate to metallic articles orwater (e.g. a human or animal body). Moreover, directivity of thetransmission (or receipt) of electromagnetic waves of dipole antennasand loop antennas degrades when the antennas are placed proximate tometallic articles or water. For example, a RFID tag in the form of anemployee badge suspended proximate to the body may de-tune and/or haveits antenna directivity affected to the extent that the RFID tag becomesunreadable when the RFID tag uses dipole or loop antennas.

The various embodiments herein address the difficulties discussed aboveemploying an antenna 17 in the RFID tag 16 that is quasi-omnidirectionaland that is unaffected, or only slightly affected, by placementproximate to a metallic object or water. In particular, FIG. 2 shows aperspective view of a dual-sided patch antenna 100 in accordance with atleast some embodiments. The dual-sided patch antenna 100 comprises afirst radiative patch or antenna element 18. The antenna element 18comprises a sheet of metallic material (e.g. copper) in the form of asquare or rectangle in this example. The length and width of the antennaelement 18 is dictated by the wavelength of the radio frequency signalthat will be driven to the antenna element 18 (or that will be receivedby the antenna element 18), for example driven by way of lead 19. Moreparticularly, the length and width of the antenna element 18 are each aninteger ratio of the wavelength of the signal to be transmitted (orreceived). For example, the length and width may be approximately halfthe wavelength (λ/2) or a quarter of the wavelength (λ/4).

The dual-sided patch antenna 100 also comprises a ground plane or groundelement 20. The antenna element 18 and the ground element 20 each definea plane, and those planes are substantially parallel in at least someembodiments. In FIG. 2, the ground element 20 length and width and theantenna element 18 length and width are shown to be approximately thesame; however, the ground element length and width may be larger orsmaller in other embodiments. Although the antenna element 18 and groundelement 20 may be separated by air, in some embodiments a dielectricmaterial 22 (e.g., printed circuit board material, silicon, plastic)separates the antenna element 18 from the ground element 20.

Still referring to FIG. 2, the dual-sided patch antenna 100 furthercomprises a second radiative patch or antenna element 24. Much likeantenna element 18, the antenna element 24 comprises a sheet of metallicmaterial (e.g. copper) in the form of a square or rectangle in thisexample. The antenna element 24 defines a plane, and in some embodimentsthe plane defined by antenna element 24 is substantially parallel to theplane defined by ground element 20 in some embodiments. The length andwidth of the antenna element 24 is dictated by the wavelength of theradio frequency signal that will be driven to the antenna element 24,for example driven by way of lead 25, and in some embodiments the lengthand width as between the antenna elements 18 and 24 are the same.Although the antenna element 24 may be separated from the ground element20 by air, in other embodiments a dielectric material 26 (e.g. printedcircuit board material, silicon, plastic) separates the antenna element24 from the ground element 20. Each antenna element 18, 24 comprises acentroid axis 28 (i.e., centroid being the point considered to be thecenter), and in some embodiments the centroid axis 28 of each antennaelement are substantially coaxial.

Radio frequency signals are driven to each of the antenna elements 18and 24 by way of probe feeds or feed points (i.e., the locations wherethe radio frequency signals couple to the antenna elements), such asfeed point 30 for antenna element 18 (the feed point for antenna element24 not visible in FIG. 2). The feed points are coupled to theirrespective leads 19 (for feed point 30) and 25 (for the feed point ofthe antenna element 24). The following discussion is directed to antennaelement 18 and feed point 30, but the discussion is equally applicableto antenna element 24. As illustrated, the feed point 30 resides within(internal of) an area defined by the length and width of the antenna,and the internal location of the feed point is selected based on severalcriteria. One such criterion is the impedance seen by a radio frequencysource that drives the antenna element 18. For example, shifting thefeed point toward the center of the antenna element 18 along its length(“L” in the figure) tends to lower the impedance seen by the radiofrequency source, while shifting along the length towards an edge (e.g.,edge 31) tends to increase impedance seen by the radio frequency source.Moreover, the placement of the feed point 30 also controls polarity ofthe electromagnetic wave created. For example, the feed point 30 asshown creates an electromagnetic wave whose electric field polarizationis substantially along the length L. Shifting the feed point toward acorner (e.g. corner 33), or also using a second feed point centeredalong the length, creates a circularly polarized electromagnetic wave.Thus, the feed points are internal to the length and width to meetthese, and possibly other, design criteria. The discussion now turns todirectivity of the dual-sided patch antenna.

Consider for purposes of explanation that the centroid axis 28 liesalong the 0°-180° axis in an overhead view (i.e., looking down on thelength L from above) of the dualsided antenna of FIG. 2, and thatantenna element 18 faces the 180° direction while antenna element 24faces the 0° direction. FIGS. 3A and 3B illustrate a far-field radiationpattern for each of the antenna elements 18 and 24 respectively. Inparticular, FIG. 3A shows that antenna element 18 considered alone has afar-field radiation pattern that is substantially directed along thecentroid axis away from the ground element 20. The plot of FIG. 3A isvalid for both overhead and elevational (i.e., looking horizontallytoward the width W) plots of far field radiation. Likewise, antennaelement 24 considered alone has a far-field radiation pattern that issubstantially directed along the centroid axis away from ground element20, and the plot (of FIG. 3B) is equally valid for both overhead andelevational plots of far-field radiation. Considering the far-fieldradiation patterns of antenna element 18 and antenna element 24together, the dual-sided patch antenna 100 has a quasi-omnidirectionalradiation (or reception) pattern, as illustrated in FIG. 4, with FIG. 4equally valid for both overhead and elevational plots of far-fieldradiation. Stated otherwise, the far-field radiation pattern for thedual-sided patch antenna is substantially the same in all three spatialdirections.

The far-field radiation patterns of FIGS. 3A, 3B and 4 show directivity,but one or more parameters of the physical system may affect theultimate far-field radiation pattern. For example, ground elementslarger than the antenna elements 18, 24 increase the size of the dips41A and 41B at the 90° and 270° orientations, while a ground element thesame size or slightly smaller may make the radiation pattern morecircular (as indicated by dashed lines 40A and 40B). The far-fieldradiation patterns of FIGS. 3A, 3B and 4 also show gain (in decibels(dB)), but no specific numbers except that the gain may be greater than0 dB in all directions. The actual gain values are related to parametersof the physical system such as frequency of operation and the dielectricstrength of the dielectric material 22 and 26.

Although the radiation pattern illustrated in FIG. 4 is at leastquasi-omnidirectional, an RFID tag comprising a dual-sided patchantenna, such as antenna 100, experiences less detrimental affects ontuning and directivity when placed proximate to a metallic article orwater, as compared to single-sided patch antennas, dipole antennas andloop antennas. The benefits are especially noticeable when the antennaelements 18 and 24 are electrically isolated (discussed more below),thereby limiting interaction that allows one antenna element performanceto affect the other. That is, while one antenna element 18 of theillustrative embodiments of FIG. 2 may be shielded between the metallicarticle or body and the ground element, the second antenna element 24 isrelatively unaffected by the presence of the metallic article or bodybecause of the electromagnetic isolation provided by the ground element.The amount of effect the non-shielded antenna element experiences aredependent to some extent upon how the antenna elements 18 and 24 arecoupled to the underlying components.

FIG. 5 illustrates an electrical block diagram of antenna elements 18and 24 of a dual-sided patch antenna 100 coupled to underlyingcomponents. In particular, in the embodiments of FIG. 5 the antennaelements 18 and 24 are coupled together, and are coupled to a matchingor tuning circuit 50. The purpose of the tuning circuit is to tune thetwo coupled antennas to be resonant at a particular frequency or set offrequencies. The turning circuit, in turn, is coupled to an RFID circuit52. The tuning circuit 50 and RFID circuit 52 may comprise an integratedproduct, such as the MCRF42X family of products available from MirochipTechnologies, Inc. of Chandler, Ariz. The RFID circuit 52 holds theidentification value or values, and is responsible for transmitting thevalue to the reader (i.e., through broadcasting using power from aninternal battery, or by backscatter using power from the interrogatingsignal). Embodiments as disclosed in FIG. 5 are operational, but whenthe one antenna element is placed proximate to a metallic article orwater, the detuning effects of the placement affect the other antennaelement, though not to the extent experienced by a dipole or loopantenna.

In alternative embodiments, the effects of placement of one antennaelement proximate to a metallic article or water are reduced byelectrically isolating the two antenna elements 18, 24 from each other.FIG. 6 shows an electrical block diagram of alternative embodimentswhere the two antenna elements of the dual-sided patch antenna 100 areelectrically isolated from each other by way of additional isolationcircuits. In particular, antenna 18 is coupled to tuning circuit 54,which in turn couples to an additional isolation circuit 59 and RFIDcircuit 66. In these embodiments, the isolation circuit 59 may compriseone or more of a power supply (PS) 56 and optional additional buffer 58.Likewise, antenna 24 is coupled to tuning circuit 60, which in turncouples to isolation circuit 65 and RFID circuit 66. Further in theseembodiments, the isolation circuit 65 may comprise one or more of apower supply (PS) 62 and an optional additional optional additionalbuffer 64. Operation of the power supply and buffer is discussed withrespect to antenna 18, but the discussion is equally applicable toantenna 24. When antenna 18 is not exposed to an interrogating signalfrom a RFID reader 12 (FIG. 1), the buffer 58 electrically isolates (orde-couples) the antenna element 18 from the RFID circuit 66. However,when exposed to interrogating signal, the buffer 58 couples the antenna18 to the RFID circuit 66. In active tags, a battery may be the powersupply 56 to provide power to sense electromagnetic signals received bythe antenna element 18, and to control the additional buffer 58. Becausethe power supply 56 may be self powered, the location of the powersupply 56 and the buffer 58 may be reversed. Moreover, a rectifyingcircuit may be present either in the power supply 56 or buffer 58 toconvert incoming data and commands to baseband data. Using batterypower, the buffer 58 continuously or periodically determines if antennaelement 18 is receiving an interrogating signal. If so, the buffer 58couples the antenna element 18 the RFID circuit 66 (e.g. by biasing thegate of a transistor to allow coupling of at least a portion of theinterrogating signal to the RFID circuit 66), with power to run thebuffer provided from the battery.

In semi-active and passive tags, the power supply 56 rectifies receivedpower from the interrogating signal, converts the received power todirect current (DC) (e.g. using Schottky diodes), and uses at least someof the converted power to control the buffer 58. For example, the buffer58 may be configured to electrically isolate the antenna element 18 fromthe RFID circuit 66 when no power is provided from the power supply 56(i.e., when there is no interrogating signal being received by theantenna element). When an interrogating signal is incident upon theantenna element 18, the power supply 56 extracts power from the signal,and uses the power to drive the buffer and couple the antenna element 18to the RFID circuit 66. Thus, regardless of the tag type, when aninterrogating signal is received on antenna element 18, the signal iscoupled to the RFID circuit 66, which responds to the reader 12 (FIG. 1)with an identification value.

Consider now a situation of a RFID tag 16 comprising the circuits asshown in FIG. 6, with the RFID tag located proximate to a metallicarticle or water. In particular, FIG. 7 shows an elevationalcross-sectional view of a badge 69 comprising a dual-sided patch antenna100, with the badge 69 proximate to an object being a body 67. Antennaelement 24 resides between the ground element 20 and the body 67, whileantenna element 18 faces away from the body 67. When the RFID tag 16 isexposed to an interrogating signal from a RFID reader 12, very little ifany of the interrogating signal is received by antenna element 24, andthus the buffer 64 (FIG. 6) keeps antenna element 24 de-coupled from theRFID circuit 66. However, antenna element 18 faces the oppositedirection and receives power from the interrogating signal. At least aportion of the received power is converted by power supply 56 (insemi-active and passive tags), and the buffer 58 couples the antennaelement 18 to the RFID circuit 66. Here, however, because of theelectrical isolation of the antenna element 24 from antenna element 18,any detuning effects of antenna element 24 resulting from its placementdoes not affect antenna element 18. With the situation reversed, andantenna element 18 shielded between the object and the ground element20, antenna element 24 receives the interrogating power and becomes theactive antenna element.

FIG. 8 illustrates yet still further alternative embodiments of a RFIDtag 16. In particular, in the embodiments illustrated in FIG. 8 eachantenna element 18, 24 of the dual-sided patch antenna 100 couples toits own tuning circuit and RFID circuit. Antenna element 18 couples totuning circuit 68 and RFID circuit 70, while antenna element 24 couplesto tuning circuit 72 and RFID circuit 74. Much like the embodiments ofFIG. 6, in the embodiments of FIG. 8 the detuning effects of one antennaelement being proximate to an object does not affect tuning of theantenna element on the opposite side of the ground element 20, thusachieving near total isolation of the two antenna elements. RFIDcircuits 70 and 74 may be designed and configured to hold and providethe same identification values when interrogated, or different values.Thus, when interrogated the RFID circuits 70 and 74 may respond with thesame value, or with different values. Further, the two RFID circuits maybe coupled in order to share data or to enable other functionality.

In order to address difficulties associated with reading RFID tags 16because of placement or position of the RFID tag relative to an objectand the reading antenna 14, at least some embodiments use two readingantennas positioned on opposite sides of an expected path of travel ofthe RFID tag 16. FIG. 9 illustrates a wall 80 having an aperture orportal 82 (e.g., a doorway). Dashed line 84 illustrates a centerline ofan expected path of travel of RFID tags 16 through the portal 82. Inorder to ensure that the RFID tags 16 passing through the portal 82 arenot shielded by the article or body to which they are attached, orshielded by nearby articles or bodies, in these embodiments two readingantennas are used: reading antenna 86 on a first side of the portal 82,and reading antenna 88 (only partially visible) on a second side of theportal 82, opposite the first side. Thus, for example, an employeehaving a badge with an RFID tag 16 hanging on the right side of his/herbody and traveling in the direction indicated by dashed line 84 has theRFID tag 16 read by reading antenna 86. Likewise, an employee having abadge with an RFID tag 16 hanging on the left side of his/her body andtraveling in the direction indicated by dashed line 84 has the RFID tag16 read by the reading antenna 88.

If the articles, people or animals moving through the portal 82 could beconstrained to movement in single file, the embodiments of FIG. 9 couldread most if not all RFID tags 16 passing through the portal 82;however, constraint to single-file passage through the portal 82 is notalways possible, particularly in the case of multiple people (who tendto walk side-by-side), and multiple animals (such as cattle) which tendto bunch in stressful situations (such as cattle working operations). Insuch situations, even though the RFID tag 16 may be on the same side ofthe object (i.e., article or body) as one of the reading antennas 86,88, the second object in the portal may shield the RFID tag 16 frombeing read. In order to at least partially address such concerns, otherembodiments elevate at least one of the reading antennas above thecenterline of the expected path of travel of the RFID tag 16.

FIG. 10 is an elevational view showing two animals 90A and 90 B passingthrough portal 82. As shown, the illustrative animals 90A and 90B haveRFID tags 16 attached to their left ears (but the tags may be in theright ears or other locations). Because of the side-by-side positioningof the animals 90, reading antennas at substantially the same elevationas the RFID tags 16 will be unable to read the RFID tags because theanimals' heads/bodies block or shield the antennas. To address suchsituations, the reading antennas 92 and 94 in these embodiments arepositioned above the elevation of the RFID tags 16 to be read. Thus, inthe illustrative situation of FIG. 10, while reading antenna 92 may beunable to read the RFID tags 16, reading antenna 94 is positioned to beable to read the RFID tags 16. If the RFID tags were located in eachanimal's right ear, then the situation would be reversed.

The elevation difference between the RFID tags 16 and the readingantennas 92, 94 is dependent upon the height of the object/body to whichthe RFID tag 16 is attached, and the expected location of the RFID tag16. For the illustrative animals of FIG. 10, the animals may be as tallas 4.5 to 5 feet, and the RFID tags 16 attached to each animal's ear arerelatively near the 4.5 to 5 feet (if a particular animal's head is up).Thus, the elevation difference between the RFID tags 16 and the readingantennas 92 and 94 may be on the order of a few feet. Where the animals'heads are consistently down, or where the RFID tag location issignificantly below the top of the animal, the reading antennas 92 and94 may need to be at least one to one and half time the expectedelevation of the RFID tags 16, and in some embodiments at least twicethe expected elevation of the RFID tags 16.

The various placements of the reading antennas discussed to this pointaddress many situations where shielding of the RFID tags 16 by thearticles/bodies to which they attach, or are shielded by nearbyarticles/bodies. However, there may be further situations where evenmultiple antennas and antennas at higher elevations than the RFID tags16 are unable to consistently read passing RFID tags. For example,consider two people walking side-by-side, with each person having theRFID tag 16 at chest or waist level. The height of the person along withthe placement of the RFID tags 16 may dictate an elevation differencebetween the reading antennas 92, 94 and the RFID tags 16 that is notachievable.

FIG. 11 illustrates alternative embodiments where the directivity of thereading antennas (that is, at least the main lobe of the far-fieldradiation or reception pattern) is directed upstream of the expectedpath of travel of the RFID tag 16. In particular, FIG. 11 is an overheadview of a walkway 96 (e.g. a hallway in a building, a cattle workingchute, or conveyor system) having two reading antennas 102 and 104 inoperational relationship to the walkway 96. A main lobe 103 of afar-field radiation (reception) pattern of reading antenna 102encompasses the centerline 106 of the expected path of travel, and inthe specific embodiments of FIG. 11, the main lobe 103 of the far-fieldradiation pattern is directed upstream of the location of the readingantenna 102. Likewise, the main lobe 105 of the far-field radiation(reception) pattern of reading antenna 104 encompasses the centerline106 of the expected path of travel upstream of the location of thereading antenna 102. In this way, RFID tags that are shielded from thereading antennas when the attempt is made to read the tags as they passthrough a portal are instead read as they approach the portal. Consider,for example, two people walking side-by-side as discussed in theimmediately preceding paragraph. As the two humans approach the readingantennas 102 and 104 moving in the direction as shown by arrow 106, theRFID tags at chest or waist level are exposed to one or both the readingantennas 102 and 104 for reading.

The embodiments discussed with respect to FIG. 11 are equivalentlyoperable when the main lobes of the far-field radiation patterns aredirected downstream from the position of the antennas (i.e., RFID tagsare read as they move away from the reading antennas). Moreover, theembodiments of elevating the reading antennas above the expectedelevation of the RFID tags may be combined with the upstream ordownstream directed reading antennas, such that the main lobes of thereading antennas are not only directed upstream (or downstream) of thelocation of the reading antennas, but also the main lobes are directeddownward toward the centerline of the expected path of travel. Directingthe main lobes of multiple reading antennas upstream (or downstream)increases the enhances a system's ability to read RFID tags that arepotentially shielded by objects to which the RFID tags attach, or byobjects proximate to the RFID tags.

Coupling of the RFID reader 12 (FIG. 1) to the various reading antennas(represented by antenna 14 in FIG. 1) may take many forms. For example,FIG. 12A illustrates embodiments where the RFID reader 12 couples to aset of reading antennas 14A and 14B (which reading antennas 14A and 14Bcould be any of the reading antennas 86 and 88, 92 and 94, or 102 and104). The RFID reader 12 may transmit and receive from both antennassimultaneously, or the RFID reader 12 may multiplex between the twoantennas. FIG. 12B illustrates systems where computer system 10 couplesto two RFID readers 12A and 12B, one RFID reader each for each antenna14A and 14B respectively. Here again, the reading antennas 14A and 14Bcould be any of the reading antennas 86 and 88, 92 and 94, or 102 and104.

FIG. 13 illustrates a method in accordance with at least someembodiments. In particular, the method starts (block 1300) and proceedsto attaching a RFID tag to an object (block 1304). In some embodiments,the far-field radiation pattern of the RFID tag in a direction away fromthe object is substantially unaffected by which surface of the RFID tagfaces away from the object, and is also substantially unaffected byproximity of the RFID tag to the object. Thus, in some embodiments theRFID tag comprises a dual-sided patch antenna 100, where each “surface”of the RFID tag is that portion of the tag that covers or is on the sameside as one of the antenna elements. The attaching of the RFID tag to anobject may take many forms. For example, the attaching may comprise:attaching a badge comprising an RFID tag to the object being a human;attaching the RFID tag to an object being a non-human animal; attachingthe RFID tag to an object being a non-human animal, the attaching by wayof an ear; and attaching the RFID tag to an object being a bovine, theattaching by way of an ear; or attaching the RFID tag to a metallicarticle. Moreover, the attaching may be at a particular nominal or tagelevation.

Still referring to FIG. 13, the next step in the illustrative method maybe positioning reading antennas at a portal through which the RFID tagtravels (block 1308). The positioning may take many forms. In someembodiments the reading antennas are placed on two sides of the portal,with the sides being opposite in some cases. Further, at least of thereading antennas may be positioned at an elevation above the expectedtag elevation, and in some cases both reading antennas are positioningabove the tag elevation. Further, in some embodiments main lobes of thefar-field radiation patterns of the reading antennas are directedupstream or downstream of the expected path of travel. Further still,the reading antennas may be placed at elevations higher than the tagelevation, and have their main lobes directed upstream or downstream.Finally, the RFID tag is read by at least one of the reading antennas(block 1312), and the illustrative process ends (block 1316).

Still referring to FIG. 13, a next step in the illustrative method isreading the RFID tag using at least one of a pair of reading antennas(block 1308). The reading may take many forms. In some embodiments, thereading is by a pair of reading antennas positioned on opposite sides ofa portal through which the RFID tags move. In other embodiments, thereading antennas are positioned above the expected elevation of the RFIDtags (i.e., are downward looking). In yet still other embodiments, thereading antennas are positioned such that their directivity (i.e., atleast the main lobe of the far-field radiation or reception pattern) isdirected upstream of an expected path of travel, and also encompassesthe centerline of the expected path of travel. In other embodiments, thereading antennas are positioned such that their directivity (i.e.,far-field radiation or reception pattern) is directed downstream of anexpected path of travel, and also encompasses the centerline of theexpected path of travel. Thereafter, the process ends (block 1312).

The dual-sided patch antenna 100 of FIG. 2 may be constructed in severalways. In some embodiments, the antenna 100 may be constructed usingflexible sheets of metallic and dielectric material adhered together andcut to appropriate dimensions. In alternative embodiments, the antenna100 may be manufactured, such as by deposition of the metallic portionsand growth of dielectric portions by way of semiconductor manufacturingtechniques. In yet still other embodiments, the antenna 100 may beconstructed using a combination of techniques, such as depositingmetallic layers on a dielectric material such as a printed circuit board(PCB), and then mechanically coupling two or more PCBs to form theantenna.

The above discussion is meant to be illustrative of the principles andvarious embodiments of the present invention. Numerous variations andmodifications will become apparent to those skilled in the art once theabove disclosure is fully appreciated. Further, while the antenna 100 isshown with a single ground element 20, the dual-sided patch antenna 100may be manufactured by adhering two patch antennas back-to-back, meaningthat two ground elements may be present, yet same advantages achieved.Moreover, significant advantages can be achieved with the antennaplacement as described herein in combination with RFID tags havingantennas other than the dual-sided patch antennas (e.g. dipole and loopantennas). It is intended that the following claims be interpreted toembrace all such variations and modifications.

1. A system comprising: a first reading antenna; a tag reader coupled tothe first reading antenna; and a radio frequency identification (RFID)tag comprising a tag antenna electromagnetically coupled to the firstreading antenna, the RFID tag coupled to an object being one or moreselected from the group consisting of: a body of a living organism; anda metallic article; and wherein the tag antenna includes a first antennaelement and a second antenna element each configured to emit far-fieldradiation patterns, the tag antenna when coupled to the object having afar-field radiation pattern in a direction away from the object that is:substantially unaffected by proximity of the RFID tag to the object; andsubstantially unaffected by which surface of the RFID tag faces theobject, wherein a ground element is disposed between the first antennaelement and the second antenna element of the tag antenna.
 2. The systemas defined in claim 1 further comprising: wherein the first readingantenna is offset in a first direction from a centerline of an expectedpath of travel of the RFID tag; and a second reading antenna offset in asecond direction, different from the first direction, from thecenterline of the expected path of travel.
 3. The system as defined inclaim 2 wherein the second direction is opposite the first direction. 4.The system as defined in claim 2 wherein at least one of the first orsecond reading antennas are mounted at an elevation above an expectedelevation of the RFID tag.
 5. The system as defined in claim 2 furthercomprising a main lobe of a far-field radiation pattern of the firstreading antenna encompasses the centerline of the expected path oftravel at a location upstream of the location of the first readingantenna.
 6. The system as defined in claim 5 further comprising a mainlobe of a far-field radiation pattern of the second reading antennaencompasses the centerline of the expected path of travel at a locationupstream of the location of the second reading antenna.
 7. The system asdefined in claim 2 further comprising a main lobe of a far-fieldradiation pattern of the first reading antenna encompasses thecenterline of the expected path of travel at a location downstream ofthe location of the first reading antenna.
 8. The system as defined inclaim 7 further comprising a main lobe of a far-field radiation patternof the second reading antenna encompasses the centerline of the expectedpath of travel at a location downstream of the location of the secondreading antenna.
 9. The system as defined in claim 1 wherein the tagantenna further comprises: a ground plane; a first antenna elementsubstantially parallel to the ground plane; and a second antenna elementsubstantially parallel to the ground plane on an opposite side of theground plane from the first antenna element.
 10. A method comprisingattaching a radio frequency identification (RFID) tag to an object, theRFID tag having a far-field radiation pattern away from the object thatis: substantially unaffected by which surface of the RFID tag faces awayfrom the object; and substantially unaffected by proximity of the RFIDtag to the object, the RFID tag including a first antenna element and asecond antenna element each configured to emit far-field radiationpatterns when not attached to the object, wherein a ground element isdisposed between the first antenna element and the second antennaelement of the tag antenna.
 11. The method as defined in claim 10wherein attaching further comprises one or more selected from the groupconsisting of: attaching a badge comprising an RFID tag to the objectbeing a human; attaching the RFID tag to the object being a non-humananimal; attaching the RFID tag to the object to a non-human animal, theattaching by way of an ear; and attaching the RFID tag to the objectingbeing a bovine, the attaching by way of an ear; attaching the RFID tagto a metallic object.
 12. The method as defined in claim 10 furthercomprising reading the RFID tag using at least one of a pair of readingantennas.
 13. The method as defined in claim 12 wherein reading furthercomprises reading using at least one of the pair of reading antennaspositioned above the elevation of the RFID tag.
 14. The method asdefined in claim 13 wherein reading further comprises reading where eachof the pair of reading antennas is oriented such that a directivity ofthe reading antenna is directed upstream of the reading antennas alongan expected path of travel of the RFID tag.
 15. The method as defined inclaim 13 wherein reading further comprises reading where each of thepair of reading antennas is oriented such that a directivity of thereading antenna is directed downstream of the reading antennas along anexpected path of travel of the RFID tag.
 16. The method as defined inclaim 12 wherein reading further comprises reading using at least one ofthe pair of reading antennas, the reading antennas positioned onopposite sides of a portal through which the RFID tag passes.
 17. Themethod as defined in claim 10 wherein attaching further comprisesattaching the RFID tag having a tag antenna comprising a ground plane, afirst antenna element substantially parallel to the ground plane, and asecond antenna element substantially parallel to the ground plane on anopposite side of the ground plane from the first antenna element.
 18. Asystem comprising: an antenna system comprising: a first antenna coupledon a first side of a portal; a second antenna, unconnected to the firstantenna, coupled on a second side of a portal, different from the firstside; a tag reader coupled to the antenna system; and a radio frequencyidentification (RFID) tag coupled to an object and electromagneticallycoupled to the antenna system by way of a dual-sided patch antenna. 19.The system as defined in claim 18 wherein the first antenna is mountedat an elevation above an expected elevation of the RFID tag.
 20. Thesystem as defined in claim 18 wherein the second side of the portal isopposite the first side of the portal.
 21. The system as defined inclaim 18 further comprising a main lobe of a far-field radiation patternof the first antenna encompasses the centerline of an expected path oftravel of the RFID tag at a location upstream of the location of thefirst antenna.
 22. The system as defined in claim 18 further comprisinga main lobe of a far-field radiation pattern of the first antennaencompasses the centerline of an expected path of travel of the RFID tagat a location downstream of the location of the first antenna.
 23. Amethod comprising: placing a radio frequency identification (RFID) tagon an object, the RFID tag comprising a dual-sided patch antenna;positioning a first reading antenna on a first side of a portal; andpositioning a second reading antenna, unconnected to the first readingantenna, on a second side of the portal.
 24. The method as defined inclaim 23 further comprising: wherein placing further comprises placingthe RFID tag at a nominal elevation; wherein positioning the first andsecond reading antennas further comprises positioning the first readingantenna at a first elevation, and positioning the second reading antennaat a second elevation, at least one of the first or second elevationshigher than the nominal elevation.
 25. The method as defined in claim 24further comprising positioning the first and second reading antennassuch that both the first and second elevations are above the nominalelevation.
 26. The method as defined in claim 23 wherein positioning thesecond reading antenna further comprises positioning the second readingantenna on the second side being opposite the first side.
 27. The methodas defined in claim 23 further comprising directing a main lobe of afar-field radiation pattern of the first reading antenna, the directingbeing one of the group consisting of: directing upstream of an expectedpath of travel of the RFID tag; and directing downstream of an expectedpath of travel of the RFID tag.
 28. The method as defined in claim 27further comprising directing a main lobe of a far-field radiationpattern of the second reading antenna, the directing being one of thegroup consisting of: directing upstream of an expected path of travel ofthe RFID tag; and directing downstream of an expected path of travel ofthe RFID tag.
 29. The method as defined in claim 27 further comprising:wherein placing further comprises placing the RFID tag at a nominalelevation; wherein positioning the first and second reading antennasfurther comprises positioning the first reading antenna at a firstelevation, and positioning the second reading antenna at a secondelevation, at least one of the first or second elevations higher thanthe nominal elevation.
 30. A method comprising: placing a radiofrequency identification (RFID) tag on an object at a tag elevation;positioning a first reading antenna on a first side of a portal at afirst elevation; and positioning a second reading antenna, unconnectedto the first reading antenna, on a second side of the portal oppositethe first side, and the positioning the second reading antenna at asecond elevation; wherein at least one of the first or second elevationsis higher than the tag elevation.
 31. The method as defined in claim 30wherein positioning the first and second reading antennas furthercomprises positioning both the first and second reading antennas abovethe tag elevation.
 32. The method as defined in claim 30 furthercomprising directing a main lobe of a far-field radiation pattern of thefirst reading antenna upstream of an expected path of travel of the RFIDtag.
 33. The method as defined in claim 32 further comprising directinga main lobe of a far-field radiation pattern of the second readingantenna upstream of an expected path of travel of the RFID tag.
 34. Asystem comprising: a first receiver antenna; a receiver coupled to thefirst receiver antenna; and a portable communications device comprisinga device antenna electromagnetically coupled to the first receiverantenna, the communications device associated with a living organism;and wherein the device antenna includes a first antenna element and asecond antenna element configured to emit far-field radiation patterns,the device antenna having a far-field radiation pattern in a directionaway from the living organism that is: substantially unaffected byproximity of the communications device to the living organism; andsubstantially unaffected by which surface of the communications devicefaces the living organism, wherein a ground element is disposed betweenthe first antenna element and the second antenna element of the tagantenna.
 35. The system as defined in claim 34 further comprising:wherein the first receiver antenna is offset in a first direction from acenterline of an expected path of travel of the communications device;and a second receiver antenna offset in a second direction, differentfrom the first direction, from the centerline of the expected path oftravel.
 36. The system as defined in claim 35 wherein the seconddirection is opposite the first direction.
 37. The system as defined inclaim 35 wherein the first receiver antenna is mounted at an elevationabove an expected elevation of the communications device.
 38. The systemas defined in claim 35 further comprising a main lobe of a far-fieldradiation pattern of the first receiver antenna encompasses thecenterline of the expected path of travel at a location upstream of thelocation of the first receiver antenna.
 39. The system as defined inclaim 38 further comprising a main lobe of a far-field radiation patternof the second receiver antenna encompasses the centerline of theexpected path of travel at a location upstream of the location of thesecond receiver antenna.
 40. The system as defined in claim 35 furthercomprising a main lobe of a far-field radiation pattern of the firstreceiver antenna encompasses the centerline of the expected path oftravel at a location downstream of the location of the first receiverantenna.
 41. The system as defined in claim 40 further comprising a mainlobe of a far-field radiation pattern of the second receiver antennaencompasses the centerline of the expected path of travel at a locationdownstream of the location of the second receiver antenna.
 42. Thesystem as defined in claim 34 wherein the device antenna comprises apatch antenna.
 43. The system as defined in claim 34 wherein thecommunications device is active.
 44. The system as defined in claim 34wherein the communications device stores identification information. 45.The system as defined in claim 34 wherein the communications devicestores identification information relating to the living organism.